Digital radio relay system

Abstract

A radio relay system for a fully-digitalized transmission network is disclosed. In the system, a received auxiliary signal can be by-passed from receiver to transmitter via a switching circuit provided in the auxiliary unit when an additional auxiliary signal is not input to the equipment. When a local auxiliary signal, for example, order wire signal from telephone equipment, is input, the switching circuit operatively disconnects the switching circuit and switches to supply the additional auxiliary signal to the transmitter. The auxiliary unit is thus by-passed upon the occurrence of a failure of the built-in circuit or power supply of the auxiliary unit.

I claim: 
     
       1. A digital radio repeating system operatively connected to receive a local auxiliary signal, comprising: a digital radio unit, comprising: receiving means for receiving time-division multiplexed digital main and first auxiliary signals sent from a precedent station and for separating the first auxiliary signal; and   transmitting means for transmitting the digital main signal and one of the first auxiliary signal and a second auxiliary signal to a subsequent station, said transmitting means including multiplexing means for multiplexing the digital main signal and one of the first and second auxiliary signals under a time-division multiplex mode; and     an auxiliary unit, operatively connected to said multiplexing and receiving means and to receive the local auxiliary signal, for generating the second auxiliary signal based on the local auxiliary signal and the first auxiliary signal which is sent from the precedent station and is separated in said digital radio unit, said auxiliary unit including detection means for detecting a failure of said auxiliary unit, said auxiliary unit ordinarily sending the second auxiliary signal to said multiplexing means for multiplexing with the digital main signal and said auxiliary unit sending the first auxiliary signal from the precedent station to said multiplexing means for multiplexing with the digital main signal for transmission to the subsequent station when said detection means detects the failure of said auxiliary unit.   
     
     
       2. The digital radio repeating system as recited in claim 1, wherein said auxiliary unit comprises by-pass means for by-passing the first auxiliary signal, as separated in said receiving means directly to said multiplexing means when the failure of said auxiliary unit is detected, whereby the digital main signal and the first auxiliary signal are transmitted to the subsequent station under the time-division multiplex mode. 
     
     
       3. A digital radio repeating system as recited in claim 1, wherein the first auxiliary signal is a digital signal produced by converting an analog signal. 
     
     
       4. A digital radio repeating system as recited in claim 1, wherein the first auxiliary signal is a digital signal representing digital data. 
     
     
       5. A digital radio repeating system as recited in claim 1, wherein said auxiliary unit includes a hybrid circuit operatively connected to said receiving means, said detection means, said multiplexing means and to receive the local auxiliary signal. 
     
     
       6. A digital radio repeating system as recited in claim 1, wherein the digital main and auxiliary signals are transmitted using Phase Shift Keying modulation. 
     
     
       7. A digital radio repeating system as recited in claim 1, wherein the digital main and first and second auxiliary signals are transmitted using Quadrature Amplitude Modulation. 
     
     
       8. A digital radio repeating system as recited in claim 1, wherein the auxiliary signal is an order wire signal transmitted between an originating station and a termination station. 
     
     
       9. A digital radio repeating system as recited in claim 1, wherein the auxiliary signal is a supervisory signal identifying a network station which added the supervisory signal. 
     
     
       10. A digital radio repeating system as recited in claim 1, wherein the auxiliary signal is a control signal. 
     
     
       11. A digital radio repeating system as recited in claim 5, wherein said auxiliary unit further comprises: a decoder operatively connected to said receiving means and said hybrid circuit; and   an encoder operatively connected to said hybrid circuit, said detection means and said multiplexing means.   
     
     
       12. A digital radio repeating system as recited in claim 2, wherein said by-pass means comprises a switching circuit operatively connected to said receiving means, said multiplexing means and said detection means, said switching circuit ordinarily supplying the second auxiliary signal to said multiplexing unit and supplying the first auxiliary signal when said detection means detects the failure of said auxiliary unit. 
     
     
       13. A digital radio repeating system as recited in claim 12, wherein said by-passing means further comprises a delay circuit operatively connected to said receiving means and said switching circuit. 
     
     
       14. A digital radio repeating system as recited in claim 8, wherein said auxiliary unit further comprises: decoder means operatively connected to said receiving means; and   encoder means operatively connected to said decoder means, said detection means, said multiplexing means and to receive the local auxiliary signal.   
     
     
       15. A digital radio repeating system as recited in claim 12, further comprising an external unit, operatively connected to said detection means, for generating a manual reset signal, wherein said detection means dispatches a control signal to said switching circuit when the manual reset signal is generated, and   wherein said switching circuit supplies the first auxiliary signal to said transmitting means when the control signal is received.   
     
     
       16. A digital radio repreating system as recited in claim 12, wherein said auxiliary unit includes a power supply and said detection means detects an outage of the power supply as the failure of said auxiliary unit.